None.
1. Field of the Invention
This invention relates in general to recirculation type engine exhaust cleaning devices, and more particularly to such devices for turbocharged diesel engines that oxidize engine combustion products by combining engine exhaust gases with turbocharged, fresh air inside a temperature-controlled reactor.
2. Background Art
It has long been known that the levels of NOx, unburnt hydrocarbons and particulates in internal combustion engine exhaust can be reduced by mixing a portion of the engine exhaust with fresh air and recirculating the mixture through the engine intake for further combustion; see, for example, U.S. Pat. No. 6,032,656 to Itoyama et al., U.S. Pat. No. 6,016,788 to Kibe et al., and U.S. Pat. No. 6,112,729 to Barnes et al. In particular, devices have been disclosed for applying this concept to turbocharged diesel engines; see U.S. Pat. No. 6,038,860 to Bailey and U.S. Pat. No. 5,937,650 to Arnold. To assure proper flow of the recirculated gases, it was further known to use a restrictor valve to create a pressure differential between the engine intake and exhaust; see U.S. Pat. No. 6,089,019 to Roby et al. It was also known to use the recycled gases to reduce the operating temperature within the cylinder combustion chambers of an engine equipped with a recirculation type exhaust gas cleaning system in order to decrease the nitrogen oxide content in the exhaust gas; see U.S. Pat. No. 3,774,399 to Nohira et al.
Unlike the foregoing, the present invention includes a temperature-controlled reactor external to the engine block for mixing and reacting recycled engine exhaust gases with pressurized, fresh air in order to oxidize engine combustion products; the mixed, reacted gases are then conducted to the engine intake for recombustion. Because the reactor is remote from the cylinder combustion chambers, conditions can be optimized within the reactor for removal of NOx, unburnt hydrocarbons and particulates without compromising conditions within the cylinder combustion chambers. U.S. Pat. No. 3,991,567 to Brimer and U.S. Pat. No. 3,306,035 to Morrrell each disclosed exhaust cleaning systems of the non-recirculating type, wherein exhaust pollutants are oxidized in a combustion chamber that is external to the engine block, but in each the cleaned exhaust is directed through a tail pipe to the atmosphere instead of being recirculated back into the engine cylinders. By including an external, temperature-controlled reactor within an exhaust gas recycling device, the present invention achieves previously unattainable low levels of exhaust pollutants in a turbocharged diesel engine.
What is needed, therefore, and what my device provides, is an exhaust gas recirculation and processing device for a turbocharged diesel engine that includes a temperature-controlled reactor, remote from the cylinder combustion chambers, within which engine combustion products are mixed and reacted with pressurized, fresh air to achieve low levels of NOx, unburnt hydrocarbons and particulates in the engine exhaust. To that end, an inlet pipe is connected to receive the gaseous combustion products of a diesel engine equipped with a turbocharger. A longitudinally-extended, reactor is provided. The reactor includes a housing that contains a first, inner chamber and a second, outer chamber that substantially surrounds the inner chamber. The inner chamber communicates with the outer chamber through slotted openings. The reactor has air inlet means that communicates with the inner chamber and with the inlet pipe, and air outlet means that communicates with the outer chamber for conducting air to the engine intake manifold. Disposed within the inner chamber is a recirculated exhaust gas combustion assembly comprised of a longitudinally-extended copper tube having an inlet end and an opposite outlet end; and a longitudinally-extended, copper baffle attached to the tube. An exhaust feed pipe extends from the exhaust outlet port of the turbocharger to the inlet end of the copper tube. A reactor output pipe has a first end in communication with the outlet end of the copper tube and an opposite, second end in communication with the inlet pipe. A pressurized air pipe extends from the air outlet port of the turbocharger to the air inlet means. Inlet valve means is provided for adjusting the flow rate of gaseous combustion products from the engine through the inlet pipe. To maintain a pressure differential between the engine intake and exhaust, restrictor means is provided in communication with the outlet end of the copper tube that impedes flow of gaseous combustion products from the engine through the tube.
In order to maintain the temperature of the reactor within a temperature range that facilitates the removal of CO, NOx and unburnt hydrocarbons, heat exchanger means is thermally coupled to the reactor exhaust outlet pipe and exchanges heat with the engine cooling system. Preferably, the reactor temperature is maintained between 124 and 195 degrees Fahrenheit for best removal of pollutants.
In a first embodiment of the device, the baffle comprises two flat, longitudinally-disposed, copper vanes attached to an exterior surface of the copper tube. In an alternative embodiment, the baffle comprises a plurality of radially and longitudinally-disposed, copper vanes attached to an exterior surface of the copper tube.
The inlet valve means includes a first valve assembly that restricts gaseous flow through the inlet pipe during cold start up of the engine, and thereafter, when engine temperature reaches a desired operating temperature, permits flow of gaseous engine combustion products through the inlet pipe and into the copper tube. The inlet valve means further includes a second valve assembly that permits flow of gaseous engine combustion products through the engine exhaust pipe during cold start up of the engine, and thereafter, when engine temperature reaches a desired operating temperature, substantially diverts flow into the inlet pipe and thence into the copper tube.
The first valve assembly includes a first, normally closed, butterfly valve, a first linear actuator coupled to said valve, and means for energizing said actuator to open said valve when the engine is at or above a desired operating temperature. The second valve assembly includes a second, normally open, butterfly valve, a second linear actuator coupled to said valve, and means for energizing said actuator to close said valve when the engine is at or above a desired operating temperature. An electrical control sytem for controlling the inlet valve means is provided, which can be either manually or automatically controlled.